Synthesis of Hydride Tantalabenzocyclopentene and µ-Alkylidene Complexes by Direct Alkylation Reactions of [TaCp*Cp′Cl2] − NMR Spectroscopic Study and X-ray Crystal Structure of [TaCp*Cp′(H)(η2-CH2-CMe2-o-C6H4)], (Cp* = η5-C5Me5; Cp′ = η5-C5H4SiMe3)

Abstract

The reaction of [TaCp*Cp′Cl2] with 1 equiv. of [Mg(CH2C6H5)2(THF)2] or 2 equiv. of LiCH2R (R = SiMe3, CMe3) leads to the formation of bis(µ‐alkylidene) complexes [(TaCp*Cp′)2(µ‐CHR)2], (R = C6H5, 1; SiMe3, 2; CMe3, 3), whereas the alkylation of [TaCp*Cp′Cl2] with 2 equiv. of LiCH2CMe2Ph gives the hydride tantalabenzocyclopentene complex [TaCp*Cp′(H)(η2‐CH2−CMe2‐o‐C6H4)] (4). All the complexes were characterized by IR and NMR spectroscopy. The molecular structure of complex 4 has been determined by X‐ray diffraction methods. Complex 4 crystallizes in the monoclinic space group P21/c, with unit cell dimensions of a = 8.976(1) Å, b = 16.596(1) Å, c = 17.929(1) Å, β = 99.26(1)°, V = 2636(1) Å3, Z = 4, ρcalcd. = 1.478 g·cm−3, R1 = 0.0481 and wR2 = 0.133. (© Wiley‐VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

The chemistry of the carbon–transition metal double and triple bond: annual survey covering the year 2002

“…The dialkyl complex 210 was obtained upon protonation. Tantalum-carbene complexes were suggested as intermediates in the formation of -alkylidene-ditantalum complexes from alkylation of tantalacene dichlorides [456]. A single paper reporting on the synthesis of both silylcarbene-tantalum complexes and silylcarbyne-tungsten complexes appeared in 2002 [457].…”

“…butylcarbene complex 455) afforded a four-membered ring derivative (e.g. 458) in a process involving Michael addition followed by intramolecular reaction of the resulting enamine (456) with the carbene complex. Analogous reaction of neutral iminoyl chlorides (e.g.…”